There has been much development over the last thirty years in the field of hook-and-loop fasteners. Early touch fastener products of this type consisted of two mating tapes, each being knit or woven. One tape would include loops of filament woven into a base, and the other would include filaments woven to form loops and then cut to form hooks. In some cases free ends of drawn plastic filaments on the male tape would be melted to form protruding heads. This shape of fastener element is sometimes called a “mushroom”, to distinguish it from “hook”-shaped elements with re-entrant crooks. In some cases, arrays of similar discrete fastening elements on two parts are shaped to engage with each other to form a releasable closure, these being known as “self-engageable” hooks or closures.
More recently, continuous molding of fastener elements extending from a common sheet-form resin base has resulted in less expensive and thinner male tapes. Significant improvements in this area include the development of continuous fastener tape molding using fixed mold cavities (see Fischer, U.S. Pat. No. 4,794,028), and the ability to provide loops on the back side of the male fastener tape as the fastener tape substrate and elements are being formed (see Kennedy et al., U.S. Pat. No. 5,260,015), thus creating a composite fastener tape capable of fastening to itself. Further improvements have reduced the size of the fastener elements moldable by such techniques, to heights of 0.015 inch or less, which provide a very smooth touch when arranged in dense arrays.
Another example of molded fastener tape involves molding perform stems or similar structures integral with a plastic backing substrate, and thereafter performing a forming operation to convert outer portions to a J hook, a mushroom head or similar engaging structure.
As molded fastener tape has been improved to be more flexible and less expensive, it has found application in disposable garments, such as diapers. Further improvements are desirable to extend the applicability of molded touch fastener products to other uses.
One such use that is discussed in more detail below is as a closure for reclosable bags and other such packaging.
Other types of repeated use closures for bags have included, for instance, rib-and-groove type of locking or zipper closures such as are marketed under the name ZIPLOC. These have very different fastening characteristics and exacting requirements for joining to sheet or film in comparison to touch-fastener closures. For example, on zipper style (interlocking rib and groove) products, in order to maintain alignment and the integrity of the seal once it is closed, the ends of such a closure are required to be permanently closed and sealed, to provide a beginning point for effecting closure. Other limitations relating to manufacture and use are also known.